Conventionally, an internal combustion engine such as a gasoline engine is provided with a camshaft for opening and closing valves. There is known a camshaft that can axially move depending on the engine operating condition. As a sensor apparatus for detecting the position of the axially movable camshaft, there is provided a sensor apparatus including a position sensor arranged in an opposing relationship with the outer circumferential surface of a camshaft (see, e.g., JP2001-65371A).
In this sensor apparatus, if the camshaft is misaligned in a radial direction, the distance between the camshaft and the position sensor is deviated from a predetermined design value, thereby generating an error in a position detection signal outputted from the position sensor. As a result, the sensor apparatus of the prior art example mentioned above may possibly be incapable of accurately detecting the axial position of the camshaft if there occurs radial misalignment of the camshaft.